[v3,1/8] iio: stx104: Implement get_multiple callback

The Apex Embedded Systems STX104 series of devices provides 4 TTL
compatible lines of inputs accessed via a single 4-bit port. Since four
input lines are acquired on a single port input read, the STX104 GPIO
driver may improve multiple input reads by utilizing a get_multiple
callback. This patch implements the stx104_gpio_get_multiple function
which serves as the respective get_multiple callback.

Cc: Jonathan Cameron <jic23@kernel.org>
Cc: Hartmut Knaack <knaack.h@gmx.de>
Cc: Lars-Peter Clausen <lars@metafoo.de>
Cc: Peter Meerwald-Stadler <pmeerw@pmeerw.net>
Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
---
 drivers/iio/adc/stx104.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

On Sat, 17 Mar 2018 11:49:56 -0400
William Breathitt Gray <vilhelm.gray@gmail.com> wrote:

> The Apex Embedded Systems STX104 series of devices provides 4 TTL
> compatible lines of inputs accessed via a single 4-bit port. Since four
> input lines are acquired on a single port input read, the STX104 GPIO
> driver may improve multiple input reads by utilizing a get_multiple
> callback. This patch implements the stx104_gpio_get_multiple function
> which serves as the respective get_multiple callback.
> 
> Cc: Jonathan Cameron <jic23@kernel.org>
> Cc: Hartmut Knaack <knaack.h@gmx.de>
> Cc: Lars-Peter Clausen <lars@metafoo.de>
> Cc: Peter Meerwald-Stadler <pmeerw@pmeerw.net>
> Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
This one is simple so applied to the togreg branch of iio.git and pushed
out as testing for the autobuilders to play with it.

Thanks,

Jonathan

> ---
>  drivers/iio/adc/stx104.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/drivers/iio/adc/stx104.c b/drivers/iio/adc/stx104.c
> index 17b021f33180..0662ca199eb0 100644
> --- a/drivers/iio/adc/stx104.c
> +++ b/drivers/iio/adc/stx104.c
> @@ -233,6 +233,16 @@ static int stx104_gpio_get(struct gpio_chip *chip, unsigned int offset)
>  	return !!(inb(stx104gpio->base) & BIT(offset));
>  }
>  
> +static int stx104_gpio_get_multiple(struct gpio_chip *chip, unsigned long *mask,
> +	unsigned long *bits)
> +{
> +	struct stx104_gpio *const stx104gpio = gpiochip_get_data(chip);
> +
> +	*bits = inb(stx104gpio->base);
> +
> +	return 0;
> +}
> +
>  static void stx104_gpio_set(struct gpio_chip *chip, unsigned int offset,
>  	int value)
>  {
> @@ -342,6 +352,7 @@ static int stx104_probe(struct device *dev, unsigned int id)
>  	stx104gpio->chip.direction_input = stx104_gpio_direction_input;
>  	stx104gpio->chip.direction_output = stx104_gpio_direction_output;
>  	stx104gpio->chip.get = stx104_gpio_get;
> +	stx104gpio->chip.get_multiple = stx104_gpio_get_multiple;
>  	stx104gpio->chip.set = stx104_gpio_set;
>  	stx104gpio->chip.set_multiple = stx104_gpio_set_multiple;
>  	stx104gpio->base = base[id] + 3;

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On Sat, Mar 17, 2018 at 5:49 PM, William Breathitt Gray
<vilhelm.gray@gmail.com> wrote:
> The Apex Embedded Systems STX104 series of devices provides 4 TTL
> compatible lines of inputs accessed via a single 4-bit port. Since four
> input lines are acquired on a single port input read, the STX104 GPIO
> driver may improve multiple input reads by utilizing a get_multiple
> callback. This patch implements the stx104_gpio_get_multiple function
> which serves as the respective get_multiple callback.

> +static int stx104_gpio_get_multiple(struct gpio_chip *chip, unsigned long *mask,
> +       unsigned long *bits)
> +{
> +       struct stx104_gpio *const stx104gpio = gpiochip_get_data(chip);
> +

> +       *bits = inb(stx104gpio->base);

I think on LE and BE if will give you different results.

> +
> +       return 0;
> +}

On Sat, Mar 17, 2018 at 08:51:07PM +0200, Andy Shevchenko wrote:
>On Sat, Mar 17, 2018 at 5:49 PM, William Breathitt Gray
><vilhelm.gray@gmail.com> wrote:
>> The Apex Embedded Systems STX104 series of devices provides 4 TTL
>> compatible lines of inputs accessed via a single 4-bit port. Since four
>> input lines are acquired on a single port input read, the STX104 GPIO
>> driver may improve multiple input reads by utilizing a get_multiple
>> callback. This patch implements the stx104_gpio_get_multiple function
>> which serves as the respective get_multiple callback.
>
>> +static int stx104_gpio_get_multiple(struct gpio_chip *chip, unsigned long *mask,
>> +       unsigned long *bits)
>> +{
>> +       struct stx104_gpio *const stx104gpio = gpiochip_get_data(chip);
>> +
>
>> +       *bits = inb(stx104gpio->base);
>
>I think on LE and BE if will give you different results.

That may be true for a memcpy operation, but in this case I'm relying on
the standard C evaluation rules. I expect we should be fine with the
returned byte assigned to an unsigned long, since it'll be evaluated by
its value rather than memory representation.

William Breathitt Gray

>
>> +
>> +       return 0;
>> +}
>
>
>
>-- 
>With Best Regards,
>Andy Shevchenko
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